Actuator and articulated robot arm

Abstract

An actuator includes a housing, an output shaft arranged coaxially with the housing, and provided so as to freely rotate with respect to the housing, and a drive mechanism for rotationally driving the output shaft with respect to the housing. The drive mechanism includes a first gear, a second gear, a swing gear, a rotor magnetic circuit, and a stator magnetic circuit. The swing gear is arranged between the first gear and the second gear, and is provided so as to freely rotate about a tilting axis, which is tilted with respect to an axis of the housing. The rotor magnetic circuit is fixed to the swing gear. The stator magnetic circuit is fixed to the housing, and configured to generate an electromagnetic force of attracting or repulsing the rotor magnetic circuit, to thereby swing the swing gear.

1 . An actuator, comprising:
 a first shaft;   a second shaft arranged coaxially with the first shaft, and provided so as to freely rotate with respect to the first shaft; and   a drive mechanism for rotationally driving the second shaft with respect to the first shaft,   the drive mechanism comprising:
 a first gear including teeth directed toward one side in an axial direction, and arranged coaxially with the first shaft; 
 a second gear including teeth opposed to the teeth of the first gear, arranged coaxially with the first shaft, and fixed to the second shaft; 
 a first swing gear arranged between the first gear and the second gear, and provided so as to freely rotate about a tilting axis, which is tilted with respect to an axis of the first shaft, 
 the first swing gear comprising:
 first teeth different in number by one tooth from the teeth of the first gear, and configured to mesh with the teeth of the first gear; and 
 second teeth different in number by one tooth from the teeth of the second gear, and configured to mesh with the teeth of the second gear on an opposite side of a meshing portion of the first teeth with the teeth of the first gear in a radial direction and in the axial direction, 
 the first swing gear being configured to mesh with the first gear and the second gear at a certain tilting angle; 
 a rotor magnetic circuit fixed to the first swing gear; and 
 a stator magnetic circuit fixed to the first shaft, and configured to generate an electromagnetic force of one of attracting and repulsing the rotor magnetic circuit, to thereby swing the first swing gear. 
 
   
     
     
         2 . An actuator according to  claim 1 , wherein the rotor magnetic circuit comprises a permanent magnet magnetized in a direction of the tilting axis, and arranged so as to be opposed to the stator magnetic circuit in the radial direction. 
     
     
         3 . An actuator according to  claim 1 , wherein:
 the rotor magnetic circuit comprises a flange including a pair of protruded pieces, which are protruded from the first swing gear toward both sides in the direction of the tilting axis, and are each made of a soft magnetic material; and   the stator magnetic circuit generates an electromagnetic force of attracting the pair of protruded pieces, to thereby swing the first swing gear.   
     
     
         4 . An actuator according to  claim 1 , wherein any one of the first shaft and the second shaft comprises a housing for accommodating the drive mechanism. 
     
     
         5 . An actuator according to  claim 1 , wherein the drive mechanism further comprises a support unit configured to support the first swing gear, the support unit being brought into contact with at least one of the first gear or the second gear in the radial direction. 
     
     
         6 . An actuator according to  claim 5 , wherein the support unit is shaped so as to be brought into rolling contact with the at least one of the first gear or the second gear. 
     
     
         7 . An actuator according to  claim 1 , wherein the first gear is fixed to the first shaft. 
     
     
         8 . An actuator according to  claim 1 , wherein the first gear is fixed to the second shaft. 
     
     
         9 . An actuator according to  claim 8 , wherein:
 the first gear and the second gear are equal in number of teeth; and   the drive mechanism further comprises a joint mechanism configured to couple the first shaft and the first swing gear to each other.   
     
     
         10 . An actuator according to  claim 8 , wherein:
 the first gear and the second gear are different in number of teeth; and   the drive mechanism further comprises:
 a third gear including teeth directed toward the one side in the axial direction, arranged coaxially with the first shaft, and fixed to the second shaft; and 
 a second swing gear including third teeth different in number by one tooth from the teeth of the third gear and configured to obliquely mesh with the teeth of the third gear, and being rotatable coaxially and integrally with the first swing gear. 
   
     
     
         11 . An actuator according to  claim 1 , wherein the drive mechanism comprises a pair of drive mechanisms arranged plane symmetric across a plane perpendicular to the axis. 
     
     
         12 . An actuator according to  claim 11 , wherein the pair of drive mechanisms comprises a plurality of pairs of drive mechanisms. 
     
     
         13 . An articulated robot arm, comprising the actuator of  claim 1 , which is arranged on at least one of a plurality of joints configured to couple a plurality of links to each other.